View source for Recognition and Description of Lesions

==Introduction==
* In order to make a veterinary diagnosis, it is essential to be able to recognise an abnormality.
** From the abnormality, we should be able to formulate an differential diagnosis before arriving at a diagnosis.
* The ability to scientifically and correctly communicate the nature of an abnormality allows
** Diagnoses to be made effectively.
** Easier communication between professionals. 

==Description of Lesions==

* The very first stage in describing a lesion is to identify the '''species''' and '''tissue/ organ''' in which the lesion resides.
** The next stage is to describe "where" and "what" the lesion is; i.e. to describe the pathological changes present.
** Once the changes have been recognised and described, a diagnosis can be formulated.

===Description of Pathological Changes===

====Where is the Lesion?====

* Lesions may be decribed as: [[Image:focal leukoencephalomalacia.jpg|thumb|right|150px|Focal lesion - focal leukoencephalomalacia (Courtesy of BioMed Archive)]]
*# '''Focal'''
*#* This means the lesion involves only part of the tissue or organ.
*#* Focal lesions may be
*#** '''Solitary''' - one lesion only.
*#** '''Multifocal''' - more than one lesion is present.
*#*** Multifocal lesions may "join-up" with each other- '''"multifocal to coalescing"'''.
*# '''Diffuse''' [[Image:cutaneous lymphosarcoma.jpg|thumb|right|150px|Diffuse lesion - cutaneous lymphosarcoma (Courtesy of BioMed Archive)]]
*#* Diffuse lesions involve the whole organ or  the whole of a specified area.
*# '''Segmental'''
*#* When the lesion affects a portion of a tubular organ, for example the intestine
*# '''Miliary''' [[Image:miliary tuberculosis.jpg|thumb|right|150px|Miliary lesion - miliary tuberculosis (Courtesy of BioMed Archive)]]
*#* Multiple small lesions.

====What is the Lesion?====

* Several parameters are used to create a detailed description of a lesion.

# '''Size'''
#* Size is outlined by giving linear measurements in 2 or 3 dimensions. 
#* It may also be useful to indicate how much of the organ or tissue is involved (i.e. as a percentage).
#* Sometimes during a full PME it may be possible to also assess
#** '''Weight''' of an organ or lesion.
#*** Must relate to something! For example, relate the weight of an organ to the weight of the animal as a whole.
#** '''Volume''' of fluid 
#*** Must again be relative.
# '''Shape'''
#* Circular, oval, nodular and so on.
#* The borders of the lesion can also be considered.
#** Well or poorly defined/ demarcated
#** Regular or irregular
#** Smooth or ragged
#* It is also possible to comment on the surface of the lesion
#** E.g. flat, elevated, depressed, umbilicated, pedunclated, sessile.
# '''Colour'''
#* Can use the primary colours plus grey, brown, black, white etc
#** E.g. "reddish-brown"
#* Is the colour seen light or dark?
#* Does the lesion appear shiny or dull?
# '''Consistency'''
#* Determined by gentle and careful palpation.
#* Described by:
#** Type: soft, firm, hard
#** Degree: slight, moderate, marked
#** Cohesion: friable, elastic etc
#* Different areas of a lesion may have different consistencies (e.g. the core may be softer).
# '''Odour'''
# '''Special features'''
#* E.g. free fluid, blood, exudates etc.
# '''Appearance of the cut surface'''
#* Consistency 
#* Amount of blood flowing from cut surface
#* Any capsule and borders
# '''Description of the draining lymph node''', if present.
#* Describe as for the main lesion.



==Interpretation of Lesions==

* Following the recognition of a particular feature in the lesion, it is possible to make some interpretations of what is seen.
* Interpretation is not set in stone- each lesion varies and may be different to the generalisations made below. 

===Interpretation of Lesion Distribuution===

* If lesions are evenly spread throughout an organ, it implies an infectious cause.

===Interpretation Based on Lesion Shape===

====Raised Lesions====

* Simplistically, a raised lesion implies that something has been gained.

====Depressed Lesions====

* Depressed lesions imply that something is missing or has been lost. 
* For example:
** [[Necrosis - Pathology|Necrosis]] 
*** Once the active phase of [[Necrosis - Pathology|necrosis]] has resolved, an irregular, disrupted shape can be created by the traction of scar tissue on adjacent tissue.
** [[Disorders of Cell Growth - Pathology#Atrophy|Atrophy]]
** In the lung, collapse (lack of air).

====Flat lesions====

* The area is neither raised or depressed.
** Lesions are recognised by colour change. 
* Flat lesions can imply an acute process.
** There has not yet been time for cells or fluid to accumulate, or for cells to be lost.

====Demarcation====

* In the case of [[Neoplasia - Pathology|neoplasms]]:
** Benign [[Neoplasia - Pathology|tumours]] are often well demarcated.
*** Grow by expansion.
** Malignant  [[Neoplasia - Pathology|tumours]] tend to be less well demarcated. 
* Inflammatory lesions:
** Well demarcated lesions are often surrounded by fibrosis.
*** Implies a chronic process.
** Poorly demarcated inflammatory lesions are often more acute.

===Interpretation of Lesion Size===

* Particularly important when submitting part of a lesion to a laboratory for histopathology.
* Assessing the proportion of the organ that is involved can be important in determining the functional significance of a lesion.
** For example, one small abscess in the liver is likely to be of no significance compared to complete hepatic fibrosis associated with chronic hepatitis affecting the whole organ.

===Interpretation of Lesion Colour===

* The normal colour of organs and tissues is a net result of the relative amounts of:
** Parenchyma
** Connective tissue
** Blood
** Fat
** Other pigments.
* Note that dark colours can obscure changes associated with light colours.

====Red or red/ black====
[[Image:consolidation and haemorrhage lung.jpg|thumb|right|150px|Consolidation and haemorrhage in the lung (Courtesy of BioMed Archive)]]
* This colouration is commonly seen with an increase in the amount of blood- may indicate 
** [[Haemorrhage|Haemorrhage]]
*** Significant [[Haemorrhage|haemorrhage]] is usually very dark, since the haemoglobin is depleted of oxygen. 
** Congestion. 
* This colour change is most obvious in light coloured tissues due to the contrast in colour.
** Easily seen in e.g. brain and lung
** More  difficult to see in e.g. spleen. 
* If seen in a nodular lesion, the lesion may be
** A [[Haemorrhage#Haematoma|haematoma]].
** A vascular lesion.
** An abscess with [[Haemorrhage|haemorrhage]].

====Black or Brown/ Black====
* This pigmentation may be due to
** [[Pigmentation - Pathology#Melanin|Melanin]] 
** [[Pigmentation - Pathology#Carbon (Anthracosis)|Exogenous carbon]]
** Putrefactive bacteria
** [[Pigmentation - Pathology#Haemosiderin|Haemosiderin]].
* Examples
** If the lesion is a mass, consider a melanoma.
*** A melanin-containing neoplasm.
** If the lesion is not raised, consider melanosis. [[Image:kidney melanosis.jpg|thumb|right|150px|Melanosis in the kidney (Courtesy of BioMed Archive)]]
*** A non-neoplastic accumulation of melanocytes.
*** Common in pigmented breeds of sheep
**** E.g. in tunica intima of aorta.
** Post-mortem change
*** Hydrogen sulphide from gastro-intestinal bacteria can give black discolouration
**** Known as pseudomelanosis
** [[Pigmentation - Pathology#Haemosiderin|Haemosiderosis]] (brown to golden brown). 
*** Implies old/ chronic congestion or [[Haemorrhage|haemorrhage]].

====Green====

* Usually bile pigment. 
** Often seen post mortem in areas of [[Liver - Anatomy & Physiology|liver]] and intestine adjacent to the [[Gall Bladder - Anatomy & Physiology|gall bladder]]. 
* Some fungal pathogens also have a green - green/black colour.
** E.g of the respiratory tract.

====Yellow====

*  A diffuse yellow colour may be caused by to icterus/ jaundice (due to bilirubin), or lipidosis.
* Yellow pigmentation can be given by:
** Fat
** Bile pigment ([[Bilirubin|bilirubin]])
** Fibrin
** [[Oedema#Composition of oedema fluid|Cellular exudates]]
** [[Neoplasia - Pathology|Neoplasms]]

====White====

* Similar causes as yellow pigmentation
** Exudates
** Neoplasia
* Also due to connective tissue
** Fibrous
** Cartilage
** Bone

===Interpretation of Lesion Consistency===

====Fluid====

* Fluid may be:
** [[Oedema|'''Oedema''']]
*** Clear
** '''Serofibrinous'''
*** Contains fibrin and implies inflammation
** '''Urine'''
*** Clear
*** Distinct odour
** '''Turbid fluid'''
*** Cloudy
*** Indicates cellular elements
*** May be due to inflammation, lymphatic or neoplastic effusion.
** '''Blood'''
*** Dark red.
*** Recent [[Haemorrhage|haemorrhage]] into the body cavities is thick, and often contains clots.
*** Serosanguinous fluid (blood tinged oedema) is often seen at necropsy.
**** Is much thinner than [[Haemorrhage|haemorrhage]], and does not contain clots.
* Fluid can also accumulate post-mortem.

====Soft==== 

* This is the normal consistency for many tissues
** Especially those with little stroma or which are loosely organised.

====Firm====

* This is normal in fluid-poor, cell-rich tissues. 
* Many inflammatory or proliferative lesions will feel firm. 
* Scar tissue will increase the firmness of an organ.

====Hard====

* Implies mineral density e.g. cartilage, bone, mineral salt deposition.

==Differential Diagnosis==

* In some cases, the diagnosis is straight-forward and based on the gross appearance of the lesion.
** E.g. trauma associated lesions such as a fractured femur or ruptured spleen. 
* Some disease entities which have characteristic/ indicative lesions.
** The official term is "'''pathognomonic'''" lesions.
** For example:
*** ''Muellerius capillaris'' and ''Dictyocaulus filaria'' (lungworm) infections in sheep
*** [[Trematodes|''Fascioliasis'']] (liver fluke) in sheep and cattle.
* When the morphological appearance of a lesion is not pathognomonic, interpretation is more difficult. 
** We must therefore consider what the reasonable options would be and how these different entities might be further differentiated.
*** I.e. the '''differential diagnosis'''.
* An example: a solitary mass in an organ.
** Could be:
*** A focus of inflammation
**** [[Purulent Inflammation|Abscess]], [[Granulomatous Inflammation|granuloma]]
*** A [[Neoplasia - Pathology|neoplasm]]
*** A [[Haemorrhage#Haematoma|haematoma]]
*** A cyst.
** Considering the categories for description of the lesion should allow  a ‘most-likely’ identity to be reached, or at least a short list of possibilities to be made. 
*** Definitive diagnosis may sometimes require histology.


[[Category:General Pathology]]